In the next funding period, we will continue to use modern neuroanatomical tracing methods to analyze, in significant detail, the organization of extrageniculate visual pathways in mammals. Cats, monkeys and rats will be the primary experimental animals, however, other mammals may be used for comparative studies. Specifically, the major thrust of our research endeavors will focus upon defining the basic connections of the pretectal complex. Thus, we are presently engaged in defining the afferent systems to the complex especially from the visual cortices and the retina, as well as determining the specific targets of the complex. Concurrently, we are also examining the neurotransmitters localized within pretectal neurons and/or terminals within the complex by use of immunoreactivity to specific compounds. In addition, we plan to expand upon our recent findings about single visual cortical neurons which have axon collaterals that project both interhemispherically and to ipsilateral subcortical visual centers. These studies will be carried out both at the light and electron microscopic levels. Tracing methods include: 1) the anterograde transport of 3H-amino acids, 2) the anterograde and retrograde transport of horseradish peroxidase, and 3) the retrograde transport of fluorescent dyes. I also plan to continue to study the connections of visual centers which are closely related to the pretectal complex. Such areas include the retina, the superior colliculus, regions of the neocortex, the lateral posterior nucleus of the thalamus and certain cranial nerve neclei which receive an input from the pretectum. Detailed data regarding important midbrain visual centers such as the pretectum will, in turn, reveal something about their role in vision as well as overall brain function